Heat pipe made of composite material and method of manufacturing the same

ABSTRACT

The heat pipe made of composite material is a sealed hollow tube being a multilayer structure made of a composite material including copper and aluminum, is filled with water and has an inner surface, an evaporator end, a condenser end and a wick. The wick is attached to the inner surface of the tube. The invention provides a cost effective and lightweight heat pipe as it uses aluminum, which is cheap and light in weight. Also, the invention provides a high performance heat pipe system as it uses copper, which is highly thermally conductive. Therefore, the heat pipe is desirable for thermal management applications in a variety of products.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat pipe, and more particularly to aheat pipe made of copper and aluminum for high performance and lessweight and manufacturing cost.

2. Description of the Prior Arts

Heat pipes provide very high conductivity for transmitting heat and areused in thermal management applications in a variety of systems andproducts. With reference to FIG. 10, a conventional heat pipe is asealed hollow tube 20, is filled with water 24, is evacuated to lower anevaporation temperature of the water 24 and has an inner surface, anevaporator end 21, a condenser end 22 and a wick 23. The wick 23 isattached to the inner surface of the tube 20.

The heat pipe works on a principle of evaporative cooling of the water24. The evaporator end 21 absorbs heat from a heat source and transfersthe heat to the water 24. The water 24 absorbs the heat and evaporatesto form vapor. The vapor flows to the condenser end 22 in a direction ofarrows d1, dissipates the heat to cooling components (e.g. fins) andthen condenses to form droplets. The condensed water 24 flows back tothe evaporator end 21 in a direction of arrows d2 due to capillary forceexerted by the wick 23. Thereby, the water 24 is circulated in the tube20 and transfers heat from the evaporator end 21 to the condenser end22.

One kind of the conventional heat pipe is made of a high thermalconductivity material such as copper. However, copper has a density of8.92 grams per cubic centimeter and that results in a relatively heavyweight of the heat pipe. Besides, copper is an expensive metal and thusresults in a high cost of the heat pipe. Another kind of theconventional heat pipe is made of a lighter and less costly materialsuch as aluminum. However, aluminum gets corroded when it comes incontact with water over time. Further, aluminum and water react togenerate hydrogen gas which gets accumulated inside the heat pipe as anon-condensable gas. This results in a significant loss in performanceof the heat pipe. Accordingly, heat pipes with both less weight andmanufacturing cost and high performance are needed.

To overcome the shortcomings, the present invention provides a heat pipemade of composite material to mitigate or obviate the aforementionedproblems.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide a heat pipe madeof copper and aluminum for high performance and less weight andmanufacturing cost.

To achieve the foregoing objective, the heat pipe made of compositematerial in accordance with the present invention is a sealed hollowtube being a multilayer structure made of a composite material includingcopper and aluminum, is filled with water and has an inner surface, anevaporator end, a condenser end and a wick. The wick is attached to theinner surface of the tube. The invention provides a cost effective andlightweight heat pipe as it uses aluminum, which is cheap and light inweight. Also, the invention provides a high performance heat pipe systemas it uses copper, which is highly thermally conductive. Therefore, theheat pipe is desirable for thermal management applications in a varietyof products.

Other objectives, advantages and novel features of the invention willbecome more apparent from the following detailed description when takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in partial section of a first embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 2 is a cross sectional front view of the heat pipe made ofcomposite material in FIG. 1;

FIG. 3 is a cross sectional front view of a second embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 4 is a cross sectional front view of a third embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 5 is a cross sectional front view of a fourth embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 6 is a cross sectional front view of a fifth embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 7 is a cross sectional front view of a sixth embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 8 is a cross sectional front view of a seventh embodiment of a heatpipe made of composite material in accordance with the presentinvention;

FIG. 9 is a flow diagram of a method of manufacturing a heat pipe madeof composite material in accordance with the present invention; and

FIG. 10 is a side view in partial section of a conventional heat pipe inaccordance with the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, a heat pipe made of composite materialin accordance with the present invention is a sealed hollow tube 10being a multilayer structure made of a composite material, is filledwith water 13, is evacuated to lower an evaporation temperature of thewater 13 and has an inner surface, an evaporator end 11, a condenser end12 and a wick 16. The composite material includes a high thermalconductivity material such as copper and a lighter and less costlymaterial such as aluminum. The wick 16 is attached to the inner surfaceof the tube 10.

In a first embodiment, the tube 10 comprises an inner layer 14 and anouter layer 15. The inner layer 14 is made of copper. The outer layer 15is made of aluminum and is clad around the inner layer 14 using a methodsuch as diffusion bonding or press fitting. The wick 16 is attached toan inner surface of the inner layer 14.

With reference to FIG. 3, in a second embodiment, the tube 10A comprisesan inner layer 14A, a mid layer 17A and an outer layer 15A. The innerlayer 14 is made of copper. The mid layer 17A is made of aluminum and isclad around the inner layer 14A using a method such as diffusion bondingor press fitting. The outer layer 15A is made of copper and is cladaround the mid layer 17A using a method such as diffusion bonding orpress fitting. The wick 16A is attached to an inner surface of the innerlayer 14A.

The wick 16 may be a screen mesh wick, a groove wick or a fiber wick.FIGS. 4 to 8 show various embodiments of the wick 16. With reference toFIG. 4, the wick 16B is a screen mesh wick and has a mesh structuremounted around the inner surface of the inner layer 14B. With referenceto FIG. 5, the wick 16C is a groove wick and has multiple axial grooves.The grooves of the wick 16C are formed around the inner surface of theinner layer 14C and are rectangular in cross section. With reference toFIG. 6, the wick 16D is a groove wick and has multiple axial grooves.The grooves of the wick 16D are formed around the inner surface of theinner layer 14D and are triangular in cross section. With reference toFIG. 7, the wick 16E is both a screen mesh wick and a groove wick andhas multiple axial grooves and a mesh structure. With reference to FIG.8, the wick 16F is a fiber wick and has a fiber wick structure mountedaround the inner surface of the inner layer 14F.

With reference to FIG. 1, when the heat pipe is in operation, theevaporator end 11 contacts a heat source and the condenser end 12contacts cooling components. The water 13 absorbs heat at the evaporatorend 11 and gets evaporated to form vapor. The vapor flows to thecondenser end 12 in a direction of arrows D1, dissipates the heat to thecooling components and then condenses to form droplets. The condensedwater 13 flows back to the evaporator end 11 in a direction of arrows D2due to capillary force exerted by the wick 16. In this manner, the heattransfer effect is achieved.

The present invention provides a high performance, cost effective andlightweight heat pipe as it uses both copper and aluminum. Therefore,the heat pipe is desirable for thermal management applications in avariety of electronics products such as notebook computers, desktopcomputers, servers, LEDs, etc.

With reference to FIG. 9, a method of manufacturing a heat pipe made ofcomposite material in accordance with the present invention comprising:

Step 1. Forming a tube: an outer layer is clad around an inner layerusing a method such as diffusion bonding or press fitting to form a tubewith a multilayer structure.

Step 2. Cutting and cleaning the tube: the tube is cut to a desirablelength and is cleaned.

Step 3. Attaching a wick: a wick is attached to an inner surface of theinner layer to provide capillary force and one end of the tube is sealedthereafter.

Step 4. Evacuating the tube: the tube is evacuated.

Step 5. Filling water: water is filled into the tube and the other endof the tube is sealed thereafter.

Step 6. Subsequent processing: the tube is flattened to have arectangular cross-section or the tube is bended to form a desirableshape corresponding to a product that needs to be cooled.

Even though numerous characteristics and advantages of the presentinvention have been set forth in the foregoing description, togetherwith details of the structure and features of the invention, thedisclosure is illustrative only. Changes may be made in the details,especially in matters of shape, size, and arrangement of parts withinthe principles of the invention to the full extent indicated by thebroad general meaning of the terms in which the appended claims areexpressed.

1. A heat pipe made of composite material being a sealed hollow tubebeing a multilayer structure made of a composite material includingcopper and aluminum, evacuated, filled with water and having an innersurface, an evaporator end, a condenser end, and a wick attached to theinner surface of the tube.
 2. The heat pipe made of composite materialas claimed in claim 1, wherein the tube has an inner layer made ofcopper; and an outer layer made of aluminum and clad around the innerlayer.
 3. The heat pipe made of composite material as claimed in claim2, wherein the outer layer is diffusion bonded to the inner layer. 4.The heat pipe made of composite material as claimed in claim 2, whereinthe outer layer is press-fitted to the inner layer.
 5. The heat pipemade of composite material as claimed in claim 1, wherein the tube hasan inner layer made of copper; a mid layer made of aluminum and cladaround the inner layer; and an outer layer made of copper and cladaround the mid layer.
 6. The heat pipe made of composite material asclaimed in claim 5, wherein the mid layer is diffusion bonded to theinner layer and the outer layer is diffusion bonded to the mid layer. 7.The heat pipe made of composite material as claimed in claim 5, whereinthe mid layer is press-fitted to the inner layer and the outer layer ispress-fitted to the mid layer.
 8. The heat pipe made of compositematerial as claimed in claim 1, wherein the wick is a screen mesh wickand has a mesh structure mounted around the inner surface of the tube.9. The heat pipe made of composite material as claimed in claim 1,wherein the wick is a groove wick and has multiple axial grooves formedaround the inner surface of the tube.
 10. The heat pipe made ofcomposite material as claimed in claim 9, wherein the grooves of thewick are rectangular in cross section.
 11. The heat pipe made ofcomposite material as claimed in claim 9, wherein the grooves of thewick are triangular in cross section.
 12. The heat pipe made ofcomposite material as claimed in claim 1, wherein the wick is both ascreen mesh wick and a groove wick and has multiple axial grooves and amesh structure.
 13. The heat pipe made of composite material as claimedin claim 1, wherein the wick is a fiber wick and has a fiber wickstructure mounted around the inner surface of the tube.
 14. A method ofmanufacturing a heat pipe made of composite material comprising: a tubeforming step, wherein an outer layer is clad around an inner layer toform a tube with a multilayer structure; a wick attaching step, whereina wick is attached to an inner surface of the inner layer and one end ofthe tube is sealed thereafter; and water filling step, wherein water isfilled into the tube and the other end of the tube is sealed thereafter.15. The method of manufacturing a heat pipe made of composite materialas claimed in claim 14, wherein the outer layer is clad around the innerlayer by diffusion bonding.
 16. The method of manufacturing a heat pipemade of composite material as claimed in claim 14, wherein the outerlayer is clad around the inner layer by press fitting.
 17. The method ofmanufacturing a heat pipe made of composite material as claimed in claim14 further comprising a step of cutting the tube to a desirable lengthafter the tube forming step.
 18. The method of manufacturing a heat pipemade of composite material as claimed in claim 14 further comprising astep of cleaning the tube after the tube forming step.
 19. The method ofmanufacturing a heat pipe made of composite material as claimed in claim14 further comprising a step of evacuating the tube after the wickattaching step.
 20. The method of manufacturing a heat pipe made ofcomposite material as claimed in claim 14 further comprising asubsequent processing of flattening the tube after the water fillingstep.
 21. The method of manufacturing a heat pipe made of compositematerial as claimed in claim 14 further comprising a subsequentprocessing of bending the tube after the water filling step.
 22. Themethod of manufacturing a heat pipe made of composite material asclaimed in claim 14, wherein the wick is a screen mesh wick and has amesh structure mounted around the inner surface of the tube.
 23. Themethod of manufacturing a heat pipe made of composite material asclaimed in claim 14, wherein the wick is a groove wick and has multipleaxial grooves formed around the inner surface of the tube.
 24. Themethod of manufacturing a heat pipe made of composite material asclaimed in claim 23, wherein the grooves of the wick are rectangular incross section.
 25. The method of manufacturing a heat pipe made ofcomposite material as claimed in claim 23, wherein the grooves of thewick are triangular in cross section.
 26. The method of manufacturing aheat pipe made of composite material as claimed in claim 14, wherein thewick is both a screen mesh wick and a groove wick and has multiple axialgrooves and a mesh structure.
 27. The method of manufacturing a heatpipe made of composite material as claimed in claim 14, wherein the wickis a fiber wick and has a fiber wick structure mounted around the innersurface of the tube.